Recently, in order to further miniaturize devices, electro-optical devices such as a display device with an integrated display unit and input unit are becoming widely prevalent. Particularly, among mobile devices such as mobile phones, personal digital assistants (PDAs), and tablet personal computers (PCs), there is widespread use of display devices equipped with a touch panel able to detect a contact position when a finger or input stylus is made to contact a display screen.
Regarding touch panels, in the related art, various types of touch panels are known, such as the so-called resistive film (pressure-sensitive) technique and the electrostatic capacitance technique. Among these, so-called capacitive touch panels, which use an electrostatic capacitance technique that detects a contact position by detecting changes in electrostatic capacitance, are being widely used in the display devices of mobile equipment and the like.
In addition, regarding such capacitive touch panels, two types of touch panels are known: touch panels of what is called the surface capacitance type, and touch panels of the projected capacitance type. Among these, projected capacitance touch panels having a large number of electrodes arranged in a matrix in a planar view are more suitably being used, since two or more contacts (multi-touch) may be detected at the same time (for example, see PTLs 1 to 7).
Herein, a general configuration of a touch panel electrode sheet used in a touch panel that uses the projected capacitance type of the electrostatic capacitance technique of the related art will be described below with reference to FIGS. 31 to 34.
FIG. 31 is an exploded perspective view illustrating a general configuration of the principal part of the conducting sheet described in PTL 1 as an electrode sheet used in a touch panel using the projected capacitance type of the electrostatic capacitance technique.
As illustrated in FIG. 31, the conducting sheet described in PTL 1 is equipped with a first transparent substrate 312A having a first conducting part 316A in which multiple first transparent conducting patterns 318A are arranged in the X direction (row direction), and a second transparent substrate 312B having a second conducting part 316B in which multiple second transparent conducting patterns 318B are arranged in the Y direction (column direction), and is configured such that the first transparent substrate 312A and the second transparent substrate 312B are stacked.
FIG. 32(a) is a plan view illustrating an example pattern of the first conducting part 316A on the first transparent substrate 312A illustrated in FIG. 31, while FIG. 32(b) is a plan view illustrating an example pattern of the second conducting part 316B on the second transparent substrate 312B illustrated in FIG. 31.
As illustrated in FIG. 32(a), the first transparent conducting pattern 318A is configured such that multiple first large lattices 324A (X pattern electrodes) are connected in series in the X direction. Each first large lattice 324A is respectively made up of a combination of multiple small lattices 326, and at the perimeter of each edge of the first large lattices 324A, first auxiliary patterns 320A made up of multiple auxiliary lines 336A unconnected to the first large lattices 324A are formed.
Similarly, as illustrated in FIG. 32(b), the second transparent conducting pattern 318B is configured such that multiple second large lattices 324B are connected in series in a second direction. Each second large lattice 324B is respectively made up of a combination of multiple small lattices 326, and at the perimeter of each edge of the second large lattices 324B, second auxiliary patterns 320B made up of multiple auxiliary lines 336B unconnected to the second large lattices 324B are formed.
The second large lattices 324B are arranged to fill in the gaps of the first large lattices 324A when viewing the above conducting sheet from the normal direction thereof.
Also, although the shapes of the auxiliary lines differ, PTLs 2 to 5 also disclose conducting sheets very similar to PTL 1.
Additionally, FIGS. 33 and 34 are respective plan view illustrating a general configuration of the principal part of a conducting sheet used in a touch panel described in PTL 7.
Among the detecting column traces 431 of the touch panel in the conducting sheet described in FIG. 33, a pair of zigzag traces 431a/431b that are line-symmetric in the Y direction are arranged at a designated interval in the X direction, and placed so that neighboring traces become line-symmetric to each other with respect to the Y direction. Similarly, among the detecting row traces 441, a pair of zigzag traces 441a/441b that are line-symmetric in the X direction are arranged at a designated interval in the Y direction, and placed so that neighboring traces become line-symmetric to each other with respect to the X direction.
In these detecting column traces 431 and detecting row traces 441, a 45-degree angle is respectively obtained with respect to the X direction by each edge forming the zigzag, and the detecting column traces 431 and detecting row traces 441 are placed so as to be orthogonal at the midpoint of each edge forming the zigzag pattern.
In addition, in the multiple areas surrounded by the detecting column traces 431 and the detecting row traces 441, isolated traces 481a/481b are placed as dummy traces.
Also, the conducting sheet illustrated in FIG. 34 has a configuration in which branching traces 482a/482b are placed in the areas surrounded by the detecting column traces 431 and the detecting row traces 441 of a touch panel having a similar shape as FIG. 33.
Herein, the branching traces 482a are formed in the same layer as the detecting column traces 431, and both ends of the branching traces 482a are electrically connected to the detecting column traces 431. Similarly, the branching traces 482b are formed in the same layer as the detecting column traces 441, and both ends of the branching traces 482b are electrically connected to the detecting row traces 441. Also, the main portions of the branching traces 482a/482b are placed so that a 45-degree angle is obtained with respect to the Y direction or the X direction.
Additionally, PTL 7 discloses a conducting sheet not provided with the isolated traces 481a/481b or the branching traces 482a/482b illustrated in FIGS. 33 and 34, but provided with detecting traces that have a similar shape to the detecting column traces 431 and the detecting row traces 441.